/proc/stat: fix scalability of irq sum of all cpu (478735e3) · Commits · 戴 / test

In /proc/stat, the number of per-IRQ event is shown by making a sum each irq's events on all cpus. But we can make use of kstat_irqs(). kstat_irqs() do the same calculation, If !CONFIG_GENERIC_HARDIRQ, it's not a big cost. (Both of the number of cpus and irqs are small.) If a system is very big and CONFIG_GENERIC_HARDIRQ, it does for_each_irq() for_each_cpu() - look up a radix tree - read desc->irq_stat[cpu] This seems not efficient. This patch adds kstat_irqs() for CONFIG_GENRIC_HARDIRQ and change the calculation as for_each_irq() look up radix tree for_each_cpu() - read desc->irq_stat[cpu] This reduces cost. A test on (4096cpusp, 256 nodes, 4592 irqs) host (by Jack Steiner) %time cat /proc/stat > /dev/null Before Patch: 2.459 sec After Patch : .561 sec [akpm@linux-foundation.org: unexport kstat_irqs, coding-style tweaks] [akpm@linux-foundation.org: fix unused variable 'per_irq_sum'] Signed-off-by:

KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Tested-by:

Jack Steiner <steiner@sgi.com> Acked-by:

Jack Steiner <steiner@sgi.com> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/stat.c

+2 −8

Original line number	Diff line number	Diff line
		@@ -31,7 +31,6 @@ static int show_stat(struct seq_file p, void v)
		u64 sum_softirq = 0;
		unsigned int per_softirq_sums[NR_SOFTIRQS] = {0};
		struct timespec boottime;
		unsigned int per_irq_sum;

		user = nice = system = idle = iowait =
		irq = softirq = steal = cputime64_zero;
		@@ -108,13 +107,8 @@ static int show_stat(struct seq_file p, void v)
		seq_printf(p, "intr %llu", (unsigned long long)sum);

		/* sum again ? it could be updated? */
		for_each_irq_nr(j) {
		per_irq_sum = 0;
		for_each_possible_cpu(i)
		per_irq_sum += kstat_irqs_cpu(j, i);

		seq_printf(p, " %u", per_irq_sum);
		}
		for_each_irq_nr(j)
		seq_printf(p, " %u", kstat_irqs(j));

		seq_printf(p,
		"\nctxt %llu\n"

include/linux/kernel_stat.h

+4 −0

Original line number	Diff line number	Diff line
		@@ -86,6 +86,7 @@ static inline unsigned int kstat_softirqs_cpu(unsigned int irq, int cpu)
		/*
		* Number of interrupts per specific IRQ source, since bootup
		*/
		#ifndef CONFIG_GENERIC_HARDIRQS
		static inline unsigned int kstat_irqs(unsigned int irq)
		{
		unsigned int sum = 0;
		@@ -96,6 +97,9 @@ static inline unsigned int kstat_irqs(unsigned int irq)

		return sum;
		}
		#else
		extern unsigned int kstat_irqs(unsigned int irq);
		#endif

		/*
		* Number of interrupts per cpu, since bootup

kernel/irq/irqdesc.c

+15 −0

Original line number	Diff line number	Diff line
		@@ -393,3 +393,18 @@ unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
		struct irq_desc *desc = irq_to_desc(irq);
		return desc ? desc->kstat_irqs[cpu] : 0;
		}

		#ifdef CONFIG_GENERIC_HARDIRQS
		unsigned int kstat_irqs(unsigned int irq)
		{
		struct irq_desc *desc = irq_to_desc(irq);
		int cpu;
		int sum = 0;

		if (!desc)
		return 0;
		for_each_possible_cpu(cpu)
		sum += desc->kstat_irqs[cpu];
		return sum;
		}
		#endif /* CONFIG_GENERIC_HARDIRQS */

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